Abstract
Understanding the effect of high strain rate deformation on microstructure and mechanical property of metal is important for addressing its performance as high strength material. Strongly motivated by the vast industrial application potential of metals having excellent hardness, we explored the phase stability, microstructure and mechanical performance of an industrial grade high carbon steel under different compressive strain rates. Although low alloyed high carbon steel is well known for their high hardness, unfortunately, their deformation behavior, performance and microstructural evolution under different compressive strain rates are not well understood. For the first time, our investigation revealed that different strain rates transform the metastable austenite into martensite at different volume, simultaneously activate multiple micromechanisms, i.e., dislocation defects, nanotwining, etc. that enhanced the phase stability and refined the microstructure, which is the key for the observed leap in hardness. The combination of phase transformation, grain refinement, increased dislocation density, formation of nanotwin and strain hardening led to an increase in the hardness of high carbon steel.
Highlights
Multiphase high carbon steels with metastable retained austenite (RA) phase are excellent for industrial applications due to their high hardness and abrasion resistance
This work explored the mechanical stability of RA in high carbon steel samples under This work explored the mechanical stability of RA in high carbon steel samples under compressive compressive stress at different strain rates, using a combination of electron back-scattered diffraction (EBSD), X-ray diffraction (XRD), TEM and nanostress at different strain rates, using a combination of EBSD, XRD, TEM and nano-indentation indentation tests
XRD and EBSD patterns demonstrate the volume of RA at increased compressive tests
Summary
Multiphase high carbon steels with metastable retained austenite (RA) phase are excellent for industrial applications due to their high hardness and abrasion resistance. When the metastable RA in high carbon steel is subjected to harsh environmental conditions; i.e., compression [1,2], abrasion [3], impact [4], etc.; RA transforms to strain induced α0 and ε martensite [5]. The α0 martensite is found to be nucleated at the intersection of the shear bands, while the ε-martensites are formed due to the overlapping stacking faults [8] These strain-induced martensites possess more strength and hardness than austenite resulting in increasing the strain hardening ability and strengthening of the material [9,10,11,12]. We carefully chose the compressive stress lower than the fracture stress to avoid fracture or failure of the material This will help us to demonstrate the mechanical and microstructural behavior of steel at the extreme working condition. Identifying various micromechanisms and their effect on hardness at various strain rates is essential to characterize high carbon steel as a superior material for the different industrial application
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